It is desired that an unbucked log's (stem's) diameter be measured along the stem's length, along with ovality, exact profile shapes, etc. and combined with crook and bow and length to make the best possible bucking solution to an unbucked log. To do this, typically the stem must be conveyed through a sensor gathering this information as it passes through. Often times, there is insufficient room for sensor measuring on a system or the cost is too high. Scanners that scan the entire length of a stem, typically 50 to 70 feet in length, are complicated and expensive.
Measuring length only is a low cost alternative used in some instances. There typically is insufficient room for the length of the log to be measured by passing the log through a sensor site. Multiple sensor sites can be used to reduce the length but there is a limit how much the distance can be reduced. Many existing systems are still manual, i.e. an operator looks at the stem and decides how long to make the first cut, cuts the stem, and then decides how long to make the second cut, cuts the stem, then the third cut, etc. There are usually from 2 to 4 logs cut from each stem. Manually cutting stems creates undesirable amounts of waste because the last cut is usually the residual amount which could be an undesirable length for marketing reasons or a short length that is not desirable, or in the worst case a too short waste piece.